All-in all-out magnetic order and propagating spin-waves in Sm2Ir2O7

TL;DR

This study uses resonant magnetic x-ray scattering to determine that Sm2Ir2O7 has an all-in all-out magnetic order and describes its spin-wave excitations, supporting its potential as a correlated Weyl semimetal.

Contribution

It reveals the magnetic ground state of Sm2Ir2O7 as all-in all-out and characterizes its spin-wave spectrum with a minimal Hamiltonian including Heisenberg and Dzyaloshinskii-Moriya interactions.

Findings

Magnetic ground state is all-in all-out antiferromagnet.

Magnon dispersion fits a Hamiltonian with J=27.3 meV and D=4.9 meV.

Supports the potential of pyrochlore iridates as Weyl semimetals.

Abstract

Using resonant magnetic x-ray scattering we address the unresolved nature of the magnetic groundstate and the low-energy effective Hamiltonian of Sm$_2$Ir$_2$O$_7$, a prototypical pyrochlore iridate with a finite temperature metal-insulator transition. Through a combination of elastic and inelastic measurements, we show that the magnetic ground state is an all-in all-out (AIAO) antiferromagnet. The magnon dispersion indicates significant electronic correlations and can be well-described by a minimal Hamiltonian that includes Heisenberg exchange ($J=27.3(6)$ meV) and Dzyaloshinskii-Moriya interaction ($D=4.9(3)$ meV), which provides a consistent description of the magnetic order and excitations. In establishing that Sm$_2$Ir$_2$O$_7$ has the requisite inversion symmetry preserving AIAO magnetic groundstate, our results support the notion that pyrochlore iridates may host correlated Weyl semimetals.